The invention relates to a plastic housing for receiving an electrical printed circuit board according to the preamble of patent claim 1 and a procedure for mounting an electronic subassembly on a carrier body according to patent claim 5.
Increasingly, electronic subassemblies are being made with plastic housings, especially in the automotive industry, since these are considerably lighter, in particular, as well as being relatively easy and cheap to manufacture, which in turn reduces fuel consumption. To attach the plastic housing to a metal carrier body, the plastic housing generally includes a mounting flange with an opening. However, as the plastic housing is very susceptible to damage in the area of the opening as a result of the forces arising during the mounting operation as when tightening screws or riveting, a hole-strengthening metal insert is employed, as can be seen, for example, from German patent DE 90 07 621 U1 (hollow rivet 4 in FIG. 1).
However, plastic housings have the disadvantage of not being able to provide electrical connection to a metal carrier body, as is used in the automotive industry, in particular, for connecting to chassis ground. A purely friction-grip connection, provided, for example, by screwing the printed circuit board to the metal housing carrier body, does not satisfy the safety requirements of the automotive industry, as the printed circuit board cannot be totally enclosed by the plastic housing and also because a friction-grip connection such as this cannot guarantee electrical contact over the service life of the product. More particularly, the printed circuit board displays a tendency to warp slightly over time in the area of the friction-grip connection and the large contact surface required for providing electrical contact eventually disappears. Cables passed through and welded inside the plastic housing, as can be seen from German patent DE 43 30 977 C2, for example, are extremely susceptible to breakage.
For this reason, electrical wiring to the chassis is currently guided through a plug construction in the plastic housing together with the other wiring for the printed circuit board and from there connected at the screw fastening point to the metal carrier body, and thus to chassis ground, during mounting by means of a cable clamp or similar device. A plastic housing of this type with a state-of-the-art connection to chassis ground via a plug device is shown at FIG. 2. Housing 1 contains printed circuit board 2, which has an electrical connection 14 to plug device 15. In plug device 15 a grounding pin not further explained is connected to a lead 11 outside plastic housing 1 and led to flange 10 and mechanical connecting means 12 (shown as a screw). However, the cost of having a separate grounding pin such as this in the plug device, in particular the cost of the parts, and of the mounting operation, including that for lead 11 outside housing 1, is considerable. German patent DE 297 09 904 U1 describes a solution similar to this. Additional contact springs for grounding purposes are described in German patent DE 91 14 287 U1.